1 large baking potato
2 tablespoons mustard seeds
1/2 cup extra-virgin olive oil
2 tablespoons minced shallots
2 teaspoons minced garlic
2 tablespoons sherry vinegar
1 teaspoon Dijon mustard
2 teaspoons nutritional yeast
6 ounces frisée, white and light green parts only, torn into bite-size pieces (8 cups)
2 tablespoons chopped chives
1/2 cup finely grated cauliflower
Preheat the oven to 425°. Wrap the potato in foil and bake for about 1 hour, until tender. Let the potato cool, then cut into 1/2-inch dice.
Meanwhile, in a medium saucepan of boiling water, cook the mustard seeds for 5 minutes. Remove from the heat and let stand for 5 minutes. Drain well.
Wipe out the saucepan and heat 2 tablespoons of the olive oil in it. Add the shallots and garlic and cook over moderately high heat, stirring, until lightly browned, about 3 minutes. Remove from the heat and whisk in 1/4 cup of the olive oil, then whisk in the vinegar, mustard and mustard seeds. Season with salt and pepper.
In a large nonstick skillet, heat the remaining 2 tablespoons of olive oil. Add the diced potato and cook over moderately high heat, stirring occasionally, until browned and crisp in spots, about 7 minutes. Season with salt and pepper and sprinkle with the nutritional yeast.
In a large bowl, toss the potato with the frisée, chives and half of the dressing; season with salt and pepper. Transfer the salad to a platter and sprinkle the cauliflower on top. Serve the remaining dressing on the side.